1 Field of the Invention
This invention relates to a channel selecting apparatus for a color television receiving apparatus or the like which has an improved operability:
2 Description of the Related Art
FIG. 5 is a block diagram showing the formation of a general television receiving apparatus. In this diagram, a television (called TV hereinafter) wave received by an antenna 1 is amplified, has the frequency converted selectively for only a specific channel in a tuner 2, is further amplified by a video intermediate frequency circuit 3, has the video signal and audio signal detected and is demodulated. The audio signal is made to be on a sufficient signal level by an audio amplifying circuit 4 and is reproduced by a speaker 5. The video signal is projected as an image by a cathode ray tube 7 through a video amplifying circuit 6.
Said tuner 2 is a so-called tuning circuit and has a function of selecting a specific frequency. The tuning frequency is determined by varying the value of the capacity component forming the tuning circuit. In fact, a local oscillator within the tuner 2 is formed to be of a voltage controlled oscillator (VCO) type using a varactor diode (variable capacity diode) in which the capacity value is variable by the voltage. The VCO is controlled by a controlling voltage from a channel selecting circuit 8. The channel selecting circuit 8 forms a channel selecting apparatus by a well known PLL frequency synthesizer system together with an operating circuit 9. The channel selection is directed to the channel selecting circuit 8 by the user through the operating circuit 9 from an input circuit 11. The operating circuit 9 has a function of operating the frequency dividing ratio (N) of a programable frequency divider within the channel selecting circuit 8 in response to the designated channel. When the frequency dividing ratio (N) is varied, the operating circuit 9 will vary the controlling voltage given to the VCO within the tuner 2 from the channel selecting circuit 8 and will vary the local oscillation frequency of the tuner 2 so that the tuner 2 may select the designated channel. In the operating circuit 9, the information required to operate the frequency dividing ratio (N) is obtained from a memory circuit 10 and, as the information, an automatic fine tuning signal (called an AFT signal hereinafter) 12 and synchronizing signal (called a SYNC signal hereinafter)13 from the video intermediate frequency circuit 3 are used. The AFT signal 12 gives the information of a difference from the prescribed frequency of the carrier frequency in a video intermediate frequency signal (called an IF signal hereinafter) at the time of selecting the channel. Also, the AFT signal 12 gives the information as to whether there is a television broadcasting signal or not together with the SYNC signal 13. U.S. Pat. No. 4,422,096 (the inventor is John G. N. Henderson) shows an example of a channel selecting apparatus of a PLL frequency synthesizer system using an AFT signal, and also recently, such channel selecting information as, for example, a receiving channel number is combined as a character signal 14 with a video signal in the video amplifying circuit 6 and is displayed in the cathode ray tube 7.
In such formation, when the user directs such channel selection as channeling up from the present receiving channel in the input circuit 11, the channel data (that is, the frequency dividing ratio data) may be increased by one channel in the operating circuit 9 and a direction may be given to the channel selecting circuit 8. However, recently, there is a system wherein a channel having a broadcast (called a signal having channel) is memorized in the memory circuit 10 in advance so that, when the channel selection of the above mentioned channeling up is directed, the information in the memory circuit 10 may be read out and the next signal having channel may be quickly received. Also, recently, both broadcast signals can be received in order that the signal supplied to the tuner 2 may be supplied with either a TV broadcast signal or a CATV broadcast signal and may be switched by the user through the input circuit 11. That is to say, the operating circuit 9 acts to determine the received frequency by the mode (that is, the TV mode or CATV mode) determined by the user.
FIG. 6 is an explanatory view showing the frequency arrangements of channels (abbreviated as CH's hereinafter) of a TV broadcast and CATV broadcast. In FIG. 6, (a) shows the frequency arrangement of TVCH's and (b) shows the frequency arrangement of CATVCH's. The frequency bands of the video carriers of 2CH to 13CH of the TV coincide with the frequency bands of the video carriers of 2CH to 13CH of the STD broadcast of the CATV. In the other CH's, the frequency of the TVCH and the frequency of the CATVCH do not coincide with each other. That is to say, the 14CH to 69CH of the TV and the A8CH to A1CH, ACH to WCH, AACH to BBBCH and 65CH to 125CH of the CATV are CH's of frequency bands peculiar respectively to the TV and CATV. If the receiving apparatus is set, for example, at the CATV mode, a memory address fitted to the CH arrangement of the CATV will be set in the memory circuit 10 to memorize the data as to whether signals are present or not in the respective channels and to receive the next signal having channel for the direction of such channel selection as channeling up.
Table 1 shows an example of the arrangement of data as to whether signals to be memorized in said memory circuit 10 are present or not in the respective CH's of the TV. Table 2 shows an example of the arrangement of data as to whether signals in said memory circuit 10 are present or not in the respective CH's of the CATV. The mark.largecircle. represents that the signal is present and the mark x represents that the signal is not present.
TABLE 1 ______________________________________ Whether the signal is CH present or not. ______________________________________ 2 .largecircle. 3 x 4 .largecircle. 5 x ' ' ' ' ' ' ' ' 68 x 69 .largecircle. ______________________________________
TABLE 2 ______________________________________ Whether the signal is CH present or not. ______________________________________ 2 .largecircle. 3 .largecircle. 4 x 5 x ' ' ' ' ' ' ' ' ' ' ' ' ' ' 124 .largecircle. 125 .largecircle. ______________________________________
By the way, in the CATV broadcast, from the frequency relation with the TV signal, various CATV broadcasting systems are practiced and, even at present, there are several kinds of systems. In the CATV broadcast in the United States, there are three broadcasting systems of an STD broadcast, HRC broadcast and IRC broadcast. Table 3 shows video carrier frequencies (in MH.sub.z) of respective channels of the three CATV broadcasting systems. Table 4 shows video carrier frequencies (in MH.sub.z) of respective channels of the TV broadcast.
TABLE 3 ______________________________________ STD HRC IRC CH broadcast broadcast broadcast ______________________________________ 2 55.25 54.00 55.25 3 61.25 60.00 61.25 4 67.25 66.00 67.25 5 77.25 78.00 79.25 6 83.25 84.00 85.25 ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' 7 175.25 180.00 175.25 8 181.25 186.00 181.25 9 187.25 192.00 187.25 10 193.25 198.00 193.25 11 199.25 204.00 199.25 12 205.25 210.00 205.25 13 211.25 216.00 211.25 ' ' ' ' ' ' ' ' ' ' ' ' 65 469.25 468.00 469.25 66 475.25 474.00 475.25 67 481.25 480.00 481.25 ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' 123 787.25 786.00 787.25 124 793.25 792.00 793.25 125 799.25 798.00 799.25 ______________________________________
TABLE 4 ______________________________________ CH TV broadcast ______________________________________ 2 55.25 3 61.25 4 67.25 5 77.25 6 83.25 7 175.25 8 181.25 9 187.25 10 193.25 11 199.25 12 205.25 13 211.25 14 471.25 15 477.25 16 483.25 ' ' ' ' ' ' 67 789.25 68 795.25 69 801.25 ______________________________________
In the light of the Tables 3 and 4, on the TV broadcast and CATV broadcast, the broadcast frequency of the 2CH to 13CH of the TV and the broadcast frequency of the 2CH to 13CH of the STD broadcast of the CATV are the same. On the three broadcasting systems of the CATV, the broadcast frequencies of the 5CH and 6CH in the respective broadcasts of the STD broadcast, HRC broadcast and IRC broadcast are different. For example, the frequency of the 5CH is 77.25 MH.sub.z in the STD broadcast, 78 MH.sub.z in the HRC broadcast and 79.25 MH.sub.z in the IRC broadcast. It is found that the broadcast frequency is different depending on the broadcasting system. The same can be said also on the 6CH.
The relations of the broadcast frequencies of the TV, STD, HRC and IRC are shown in FIG. 7. As shown in FIG. 7(a), on the 5CH and 6CH, as described above, the respective broadcast frequencies of the STD, HRC and IRC are different. If the broadcast frequency of the STD is represented by fSTD, the broadcast frequency fHRC of the HRC will be fHRC=fSTD+0.75 MH.sub.z, the broadcast frequency fIRC of the IRC will be fIRC=fSTD+2MH.sub.z and the broadcast frequency fTV of the TV will be fTV=fSTD. Also, as shown in FIG. 7(b), on the other CH's than the 5CH and 6CH, the broadcast frequency fHRC of the HRC is fHRC=fSTD-1.25 MH.sub.z and the broadcast frequency fIRC of the IRC is fIRC=fSTD=fTV.
As such are the frequency relations, in the above described TV receiving apparatus which can receive the TV broadcast and CATV broadcast, the selection of the TV broadcast signal and CATV broadcast signal is complicated but a TV receiving apparatus provided with four receiving modes of the TV, STD, HRC and IRC is already practiced.
In the TV receiving apparatus provided with a plurality of such receiving modes, after the user sets the operating circuit 9 in the respective modes through the input circuit 11, CH data (data as to whether signals are present or not) in the memory circuit 10 will be automatically set.
FIG. 8 shows a flow chart of the operation of setting CH data in the memory circuit 10 after the receiving mode is set. By setting the receiving mode, the memory address in the CH arrangement of the CATV or TV is set in the memory circuit 10 and the process shifts to the CH data setting operation in FIG. 8. In the steps S1 to S4, first the CH is selected, whether a signal is present or not in the CH is judged, if a signal is present, data showing that a signal is present will be written into the memory circuit 10 but, if no signal is present, data showing that no signal is present will be written into the memory circuit 10. Thereafter, as shown in the steps S5 and S6, the process of increasing CH's and returning to the step S1 is repeated but, before that, whether the data have been written in is judged on all the CH's and, if they have been written in on all the CH's, the process will end.
Now, in the conventional TV receiving apparatus wherein signals can be received in a plurality of modes and, after the receiving mode is set, the CH data will be automatically set. In the case of selecting the channel of the television signal, the user will confirm in advance whether the signal connected to the antenna terminal is a TV signal or CATV signal and of which broadcasting system the CATV signal is and then will have to set the receiving mode of the receiving apparatus to be used. Thus, there has been a problem that the operability of the apparatus is low.